What is gassing off from my already double-dry wine?

[chonn]

Wine is double dry - 0.00 RS and 0 g/L of ML - and sat for a week before racking.

Racked it and then purged headspace with Argon (very aggressively/thoroughly) and over-pressured it to 2 PSI.

Every day I come back and check the pressure gauge and it gains about 1/8 PSI every 24 hours which I bleed back down to 2 PSI....if I left it for 8 days it would probably rise to 3 PSI.

Where is this extra pressure coming from?

I thought maybe co2 offgassing but co2 prefers to dissolve into wine rather than argon, yes? I don't think co2 can offgas into pressurized headspace.

I also expected an immediate bump in the pressure as the cold argon from the bottle warmed up but that doesn't explain the constant day-after-day rise.

Does anyone have any theories as to why my pressure is rising?

 

[Rice_Guy]

thought maybe co2 offgassing but co2 prefers to dissolve into wine rather than argon, yes? I don't think co2 can offgas into pressurized headspace.
Does anyone have any theories as to why my pressure is rising?

* 1/8 psig isn’t a lot, with the gauges I own that could be noise as from a manometer tube relaxing
* CO2 is trying to accomplish an equilibrium. “If the partial pressure of gas X is high it will dissolve into the wine, if the partial pressure of X is low it will leave the wine”. I would assume that argon out of a cylinder is clean / has zero pressure contributed from CO2. therefore it would evaporate from the wine into the headspace.
* my experience in contests is almost half of the wines have some bubbles on the glass. My experience using vacuum corking at -18 inches Hg is that I pull foam if I haven’t vacuum degassed for 12 to 18 hours. . . . . a normal atmospheric degassing has quite a bit of CO2 left.

 

[chonn]

* CO2 is trying to accomplish an equilibrium. “If the partial pressure of gas X is high it will dissolve into the wine, if the partial pressure of X is low it will leave the wine”. I would assume that argon out of a cylinder is clean / has zero pressure contributed from CO2. therefore it would evaporate from the wine into the headspace.

OK SO bottom line--you believe it is co2 coming out of the wine and into the headspace?

So many questions....

I guess the two that come to mind are:

1: There must be a headspace pressure of argon that would prohibit the co2 from leaving the wine. I wouldn't want that, but for my own education, that must be true, correct?

2: If the co2 leaves the wine that increases the volume of the headspace which is why the pressure rises....but doesn't it also decrease the volume of the wine? How close are those increases/decreases or are they not close at all?

Thanks very much!

 

[sour_grapes]

OK SO bottom line--you believe it is co2 coming out of the wine and into the headspace?

So many questions....

I guess the two that come to mind are:

1: There must be a headspace pressure of argon that would prohibit the co2 from leaving the wine. I wouldn't want that, but for my own education, that must be true, correct?

2: If the co2 leaves the wine that increases the volume of the headspace which is why the pressure rises....but doesn't it also decrease the volume of the wine? How close are those increases/decreases or are they not close at all?

Thanks very much!

1. No, that is not true. Eventually, there will be an equilibrium between the partial pressure of the CO2 in the headspace and the amount of CO2 dissolved in the gas. The ratio of those two things is fixed, which is the gist of Henry's Law. That ratio is not affected by the presence of other gases. (Ar, too, is subject to Henry's Law, but with a different ratio.)

2. They are not close at all. The intermolecular distance in a liquid is about one order of magnitude smaller that in gas (at ~atmospheric pressure).

 

[chonn]

Thanks--really appreciated.

 

[Rice_Guy]

The key phrase in all this is “partial pressure”. Each gas in a mixture has its own percentage of the mixture which contributes the “part” of the volume ~ pressure from molecules.
Making it complicated each gas has its own solubility in the wine and that will vary based on what gas it is, what temperature it is at, the type of wine (molecules that can ionize/ complex), and probably other traits as ReDox potential, how many atmospheres of pressure, hydrogen bonding ,,, In the practical world CO2 is quite soluble, oxygen is a little soluble and we don’t worry about others since they don’t cause problems.

 

[mikewatkins727]

Barometric pressure changes - daily.

 

[Hazelemere]

Wine is double dry - 0.00 RS and 0 g/L of ML - and sat for a week before racking.

Racked it and then purged headspace with Argon (very aggressively/thoroughly) and over-pressured it to 2 PSI.

Every day I come back and check the pressure gauge and it gains about 1/8 PSI every 24 hours which I bleed back down to 2 PSI....if I left it for 8 days it would probably rise to 3 PSI.

Where is this extra pressure coming from?

I thought maybe co2 offgassing but co2 prefers to dissolve into wine rather than argon, yes? I don't think co2 can offgas into pressurized headspace.

I also expected an immediate bump in the pressure as the cold argon from the bottle warmed up but that doesn't explain the constant day-after-day rise.

Does anyone have any theories as to why my pressure is rising?

malolactic fermentation